package org.apache.jackrabbit.demo.mu.filters;

/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

import javax.servlet.*;
import java.io.IOException;


/**
* <p>Example filter that sets the character encoding to be used in parsing the
* incoming request, either unconditionally or only if the client did not
* specify a character encoding.  Configuration of this filter is based on
* the following initialization parameters:</p>
* <ul>
* <li><strong>encoding</strong> - The character encoding to be configured
* for this request, either conditionally or unconditionally based on
* the <code>ignore</code> initialization parameter.  This parameter
* is required, so there is no default.</li>
* <li><strong>ignore</strong> - If set to "true", any character encoding
* specified by the client is ignored, and the value returned by the
* <code>selectEncoding()</code> method is set.  If set to "false,
* <code>selectEncoding()</code> is called <strong>only</strong> if the
* client has not already specified an encoding.  By default, this
* parameter is set to "true".</li>
* </ul>
* <p/>
* <p>Although this filter can be used unchanged, it is also easy to
* subclass it and make the <code>selectEncoding()</code> method more
* intelligent about what encoding to choose, based on characteristics of
* the incoming request (such as the values of the <code>Accept-Language</code>
* and <code>User-Agent</code> headers, or a value stashed in the current
* user's session.</p>
*
* @author Craig McClanahan
* @version $Revision: 1.2 $ $Date: 2004/03/18 16:40:28 $
*/
public class SetCharacterEncodingFilter implements Filter {

   // ----------------------------------------------------- Instance Variables


   /**
    * The default character encoding to set for requests that pass through
    * this filter.
    */
   protected String encoding = null;


   /**
    * The filter configuration object we are associated with.  If this value
    * is null, this filter instance is not currently configured.
    */
   protected FilterConfig filterConfig = null;


   /**
    * Should a character encoding specified by the client be ignored?
    */
   protected boolean ignore = true;

   // --------------------------------------------------------- Public Methods


   /**
    * Take this filter out of service.
    */
   public void destroy() {

       this.encoding = null;
       this.filterConfig = null;

   }


   /**
    * Select and set (if specified) the character encoding to be used to
    * interpret request parameters for this request.
    *
    * @param request The servlet request we are processing
    * @param response  The servlet response we are creating
    * @param chain   The filter chain we are processing
    * @throws IOException      if an input/output error occurs
    * @throws ServletException if a servlet error occurs
    */
   public void doFilter(ServletRequest request, ServletResponse response,
                        FilterChain chain)
           throws IOException, ServletException {

       // Conditionally select and set the character encoding to be used
       if (ignore || (request.getCharacterEncoding() == null)) {
           String encoding = selectEncoding(request);
           if (encoding != null)
               request.setCharacterEncoding(encoding);
       }

       // Pass control on to the next filter
       chain.doFilter(request, response);

   }


   /**
    * Place this filter into service.
    *
    * @param filterConfig The filter configuration object
    */
   public void init(FilterConfig filterConfig) throws ServletException {

       this.filterConfig = filterConfig;
       this.encoding = filterConfig.getInitParameter("encoding");
       String value = filterConfig.getInitParameter("ignore");
       if (value == null)
           this.ignore = true;
       else if (value.equalsIgnoreCase("true"))
           this.ignore = true;
       else this.ignore = value.equalsIgnoreCase("yes");

   }

   // ------------------------------------------------------ Protected Methods


   /**
    * Select an appropriate character encoding to be used, based on the
    * characteristics of the current request and/or filter initialization
    * parameters.  If no character encoding should be set, return
    * <code>null</code>.
    * <p/>
    * The default implementation unconditionally returns the value configured
    * by the <strong>encoding</strong> initialization parameter for this
    * filter.
    *
    * @param request The servlet request we are processing
    */
   protected String selectEncoding(ServletRequest request) {

       return (this.encoding);

   }


}